The proposed centers around a search for a useful index of ventricular contractility which has a sound physiological basis and clinical usefulness. Our previous studies on excised canine hearts indicated that the end-systolic pressure-volume relationship of the canine left ventricle is, as an approximation, independent of loading conditions and linear in the physiological range. We hypothesized that its slope (Emax) and volume axis intercept (Vd) serve good indices of contractility of the ventricle as a compression chamber. Several other groups of clinical investigators responded to this proposal with positive answers. We would continue to provide the cardiologist community with further scientific bases for using the Emax and Vd parameters to evaluate contractile state of the ventricle. The immediate effort in the 1981-1982 period will be to characterize canine models of the hypertrophied hearts and ischemic hearts in terms of the end-systolic pressure-volume relationship.